The present invention relates to a seatback frame for a vehicle seat and, more particularly, to a seatback frame for a vehicle seat equipped with a seat belt of the three-point type wherein a retractor for winding a seat belt is mounted at a lower portion of the seatback and allows a shoulder belt to be pulled out for restraining a seat occupant, a belt-through member is mounted at an upper distal end of the seatback for guiding the shoulder belt, fixture segments are mounted at both sides of a seat cushion for supporting both ends of a lap belt which restrains the waist of the seat occupant, and a distal end of the shoulder belt is supported with one of the fixture segments.
In general, seat belts in practical use are divided into two types, a first type in which a retractor is fixedly mounted to a pillar of a vehicle body and a second type in which the retractor is directly fixed to a seatback frame. The seat belt in normal use is constructed of a lap belt portion for restraining the waist of a seat occupant and a shoulder belt portion for restraining an area covering the shoulder and the waist of the seat occupant, which are arranged in a three-point support structure which includes lap anchor points located at both sides of a seat cushion and a shoulder anchor point located at an upper distal end of a seatback.
Since the vehicle seat, wherein the shoulder anchor point is located on the seatback frame, encounters a significantly large impact shock delivered from the shoulder belt and acting on the shoulder anchor point, it is required for the seatback frame to be reinforced. An example of such a seatback frame with a reinforced structure is exemplarily shown in FIG. 5. As shown in FIG. 5, the seatback frame 1 is comprised of a pipe frame 2 which is shaped to conform along an external shape of a seatback, and a tower frame 3 on which a belt-through member (not shown) for a shoulder anchor point is mounted. To provide a reinforced structure for the tower frame 3, particularly, a cross member 4 is obliquely placed so as to extend between an upper distal end of the tower frame 3 and a bracket 2a opposed thereto and welded to both of these components.
In the seatback frame 1 for the vehicle seat equipped with the seat belt of the related art practice, the cross member 4 located so as to extend from the upper distal end of the tower frame 3 toward the opposing side portion of the seatback frame for reinforcement has an increased weight, providing a degraded operability during a reclining operation of the seatback.
Further, the presence of the cross member 4 obliquely located in a substantially central area of the seatback so as to cross over the same encounters a difficulty in enhancing a space for locating an active-type headrest (which is of the type wherein when exerted with impact shocks, lower distal ends of the headrest stays are urged rearward to cause the headrest to move forward for thereby preventing the head of the seat occupant from being swayed rearward to protect the same). As a result, only a general-purpose headrest can only be employed in the seatback, with a difficulty in adopting the active type headrest with an increased functional property.
During rearward collisions, also, the tower frame 3 is exerted with the impact load and, so, is required to have the structure reinforced in forward and rearward directions. However, with such a reinforced structure using the cross member 4, although a rigidity is provided in structure in a widthwise direction of a vehicle body, a relatively unsatisfied result takes place in the presence of the impact shocks imparted in the forward and rearward directions of the vehicle body.
It is therefore an object of the present invention to provide a seatback frame, for a vehicle seat equipped with a three-point support type seat belt, which has a tower frame with a strong rigidity in structure sufficient for resisting impact load exerted thereto, which is lighter in weight than the related art cross member, and which enables an active type headrest to be employed. Furthermore, it is another object of the present invention to provide a vehicle seat to which such a seatback frame is applied.
According to an aspect of the present invention, there is provided a seatback frame for a vehicle seat having a seatback and a seat cushion and equipped with a seat belt of a three-point type, wherein a retractor is mounted at a lower portion of the seatback to wind up the seat belt, a belt-through member is mounted at an upper distal end of the seatback to guide a shoulder belt of the seat belt, which is pulled out from the retractor, so as to restrain a shoulder portion of a seat occupant, both ends of a lap belt of the seat belt, which restrain a waist portion of the seat occupant, are supported with fixed portions located at both sides of the seat cushion, and a distal end of the shoulder belt is further supported with one of the fixed portions. The seatback frame is provided with: a pipe frame formed along an external shape of the seatback; and a vertically extending tower frame located in the seatback at the same side as the belt-through member and fixedly connected to the pipe frame. The tower frame includes an outer side bracket, an inner side bracket, both of which are formed of vertically extending, elongated metal sheets each formed in a substantially C-shaped cross section and both of which are coupled to one another in abutting engagement with one another to form an internal space, and an intermediate brace member incorporated in the internal space to provide a reinforcement rib structure.
According to another aspect of the present invention, a vehicle seat is provided with: a seatback; a seat cushion; a seat belt of a three-point type, wherein a retractor is mounted at a lower portion of the seatback to wind up the seat belt, a belt-through member is mounted at an upper distal end of the seatback to guide a shoulder belt of the seat belt, which is pulled out from the retractor, so as to restrain a shoulder portion of a seat occupant, both ends of a lap belt of the seat belt, which restrain a waist portion of the seat occupant, are supported with fixed portions located at both sides of the seat cushion, and a distal end of the shoulder belt is further supported with one of the fixed portions; and a seatback frame. The seatback frame is provided with: a pipe frame formed along an external shape of the seatback; and a vertically extending tower frame located in the seatback at the same side as the belt-through member and fixedly connected to the pipe frame. The tower frame includes an outer side bracket, an inner side bracket, both of which are formed of vertically extending, elongated metal sheets each formed in a substantially C-shaped cross section and both of which are coupled to one another in abutting engagement with one another to form an internal space, and an intermediate brace member incorporated in the internal space to provide a reinforcement rib structure.
Other and further features, advantages, and benefits of the present invention will become more apparent from the following description taken in conjunction with the following drawings.